A transfer chamber for transferring substrates (wafers) stored in a cassette to a substrate support (boat) is installed in a substrate processing apparatus. The transfer chamber is purged with, for example, an inert gas such as a nitrogen gas, to suppress a natural oxide film from being formed on the wafers.
In the related art, there is a technique of purging a transfer chamber of a substrate processing apparatus with an inert gas.
When purging the transfer chamber with the inert gas such as the nitrogen gas, there is a need to reduce consumption of the nitrogen gas.